When the price of a product was decreased by $10 \%$,the number sold increased by $30 \%$. What was the effect on the total revenue (in $\%$)?

If $A$'s salary is $30\%$ more than that of $B$,then by how much percent is $B$'s salary less than that of $A$ (in $\%$)?

$A$ number,when $35$ is subtracted from it,reduces to its $80$ percent. What is four-fifths of that number?

$A$ fruit seller had some apples. He sells $40 \%$ of the apples and still has $420$ apples. Originally,how many apples did he have?

$A$ candidate appearing for an examination has to secure $35 \%$ marks to pass. But he secured only $40$ marks and failed by $30$ marks. What would be the maximum marks of the test?

If $37 \frac{1}{2} \%$ of a number is $45,$ then $87 \frac{1}{2} \%$ of the number will be: